High-power electrically pumped terahertz topological laser based on a surface metallic Dirac-vortex cavity.

Topological lasers (TLs) have attracted widespread attention due to their mode robustness against perturbations or defects. Among them, electrically pumped TLs have gained extensive research interest due to their advantages of compact size and easy integration. Nevertheless, limited studies on electrically pumped TLs have been reported in the terahertz (THz) and telecom wavelength ranges with relatively low output powers, causing a wide gap between practical applications. Here, we introduce a surface metallic Dirac-vortex cavity (SMDC) design to solve the difficulty of increasing power for electrically pumped TLs in the THz spectral range. Due to the strong coupling between the SMDC and the active region, robust 2D topological defect lasing modes are obtained. More importantly, enough gain and large radiative efficiency provided by the SMDC bring in the increase of the output power to a maximum peak power of 150 mW which demonstrates the practical application potential of electrically pumped TLs.

Discovery of betulinic acid derivatives as gut-restricted TGR5 agonists: Balancing the potency and physicochemical properties.

The pleiotropic effects of TGR5 make it an appealing target for intervention of metabolic and inflammatory disorders, but systemic activation of TGR5 faces challenges of on-target side effects, especially gallbladder filling. Gut-restricted agonists were proved to be sufficient to circumvent these side effects, but extremely low systemic exposure may not be effective in activating TGR5 since it is located on the basolateral membrane. Herein, to balance potency and physicochemical properties, a series of gut-restricted TGR5 agonists with diversified kinetophores had been designed and synthesized. Compound 22-Na exhibited significant antidiabetic effect, and showed favorable gallbladder safety after 7 days of oral administration in humanized TGR5H88Y mice, confirming that gut-restricted agonism of TGR5 is a viable strategy to alleviate systemic target-related effects.

High power, broad tuning quantum cascade laser at λ ∼ 8.9 µm.

Many molecules have broad fingerprint absorption spectra in mid-wave infrared range which requires broadly tunable lasers to cover the interested spectrum in one scan. We report a strain-balanced, InAlAs/InGaAs/InP quantum cascade laser structure based on diagonal transition active region with high output power and and wide tuning range at λ ∼ 8.9 µm. The maximum pulsed optical power and the wall-plug efficiency at room temperature are 4 W and 11.7%, respectively. Maximum continuous wave double-facet power is 1.2 W at 25 °C for a 4 mm by 9 µm laser mounted epi-side down on a diamond/copper composite submount. The maximum pulsed and continuous wave external-cavity tuning range are from 7.71 µm to 9.15 µm and from 8 µm to 8.9 µm, respectively. The continuous wave power of the external cavity mode exceeds 200 mW across the entire spectrum.

Above 20†GHz high frequency operation of mid-infrared doughnut-shaped microcavity quantum cascade lasers.

Microresonator-based high-speed single-mode quantum cascade lasers are ideal candidates for on-chip optical data interconnection and high sensitivity gas sensing in the mid-infrared spectral range. In this paper, we propose a high frequency operation of single-mode doughnut-shaped microcavity quantum cascade laser at ∼4.6 µm. By leveraging compact micro-ring resonators and integrating with grounded coplanar waveguide transmission lines, we have greatly reduced the parasitics originating from both the device and wire bonding. In addition, a selective heat dissipation scheme was introduced to improve the thermal characteristics of the device by semi-insulating InP infill regrowth. The highest continuous wave operating temperature of the device reaches 288 K. A maximum -3 dB bandwidth of 11 GHz and a cut-off frequency exceeding 20 GHz in a microwave rectification technique are obtained. Benefiting from the notch at the short axis of the microcavity resonator, a highly customized far-field profile with an in-plane beam divergence angle of 2.4° is achieved.

Biodegradation of additive-free polypropylene by bacterial consortia enriched from the ocean and from the gut of Tenebrio molitor larvae.

Accumulation of highly recalcitrant PP wastes has caused a serious environmental pollution. We evaluated the biodegradation of two types of additive-free PP polymers by microbial degraders from different environments. Two bacterial consortia, designated as PP1M and PP2G, were enriched from the ocean and from the guts of Tenebrio molitor larvae. Both consortia were able to utilize each of two different additive-free PP plastics with relatively low molecular weights (low molecular weight PP powder and amorphous PP pellets) as the sole carbon source for growth. After a 30-day incubation, several plastic characterization methods, including high-temperature gel permeation chromatography, scanning electron microscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry, were used to characterize the PP samples. The bio-treated PP powder was covered with tight biofilms and extracellular secretions with significantly increased hydroxyl and carbonyl groups and slightly decreased methyl groups. This suggested that degradation and oxidation had occurred. The altered molecular weights and the increased melting enthalpy and average crystallinity of the bio-treated PP samples all suggested that both consortia preferred to depolymerize and degrade the fractions with molecular weights of ≤34 kDa and the amorphous phase fractions of the two types of PP. Furthermore, low molecular weight PP powder was more susceptible to bacterial degradation compared to amorphous PP pellets. This study provides a unique example of different types of additive-free PP degradation by different culturable bacteria from the ocean and insect guts as well as a feasibility of PP waste removal in different environments.